title: Effects of induced hypertension on transcranial Doppler ultrasound velocities in patients after subarachnoid hemorrhage.
abstract: OBJECTIVE
  Transcranial doppler ultrasound (TCD) is used after subarachnoid hemorrhage to detect cerebral vasospasm and is often treated with induced hypertension. Cerebral autoregulation, however, may be disturbed in this population, raising the possibility that TCD velocities may be elevated by induced hypertension. To study this possibility, we performed continuous TCD monitoring of the middle cerebral artery during the induction and withdrawal of induced hypertension in patients after subarachnoid hemorrhage.
  
  
  METHODS
  Twenty-eight patients were studied during the induction and withdrawal of hypertension using primarily phenylephrine. Continuous monitoring was performed on the middle cerebral artery with the highest flow velocity. Treatment was based on rising TCD velocities or clinical evidence for cerebral vasospasm. Mean arterial pressure and mean TCD velocities were recorded every minute. A change of > 15% from starting TCD values was considered significant. Cerebral autoregulation was calculated as a percentage of intact autoregulation. Patients were subsequently divided into groups of disturbed and intact autoregulation.
  
  
  RESULTS
  In 10 of 19 patients (53%), TCD velocities changed by > 15% and paralleled changes in mean arterial pressure. This directly altered the TCD interpretation of the grade of vasospasm in 7 of 19 patients (36%). Three additional patients had smaller absolute changes in TCD velocities. No clinical difference could be identified between patients with disturbed and intact autoregulation.
  
  
  CONCLUSIONS
  In patients with disturbed autoregulation after subarachnoid hemorrhage, induced hypertension can alter cerebral blood flow velocities. The level of autoregulation needs to be considered when interpreting TCD velocities in patients after subarachnoid hemorrhage.
authors.affiliation: Neurology/Neurosurgery Intensive Care Unit, Washington University School of Medicine, St Louis, Mo 63110, USA. mannoe@neuro.wustl.edu
authors.forename: E M
authors.initials: EM
authors.lastname: Manno
authors.forename: D R
authors.initials: DR
authors.lastname: Gress
authors.forename: L H
authors.initials: LH
authors.lastname: Schwamm
authors.forename: M N
authors.initials: MN
authors.lastname: Diringer
authors.forename: C S
authors.initials: CS
authors.lastname: Ogilvy
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D006439:Hemodynamics / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis; D006801:Humans; D006973:Hypertension / Q000139:chemically induced*; D008297:Male; D008875:Middle Aged; D018579:Patient Selection; D010656:Phenylephrine; D013345:Subarachnoid Hemorrhage / Q000000981:diagnostic imaging* / Q000503:physiopathology*; D017585:Ultrasonography, Doppler, Transcranial; D014662:Vasoconstrictor Agents
chemical_list: D014662:Vasoconstrictor Agents; D010656:Phenylephrine